The shuddering could also be coming from the ABS itself. The Aurora has a little bit more safisticated braking sytem than normal cars and tend to feel like they are shuddering at times but not because the ABS is kicking in but for other reasons in the way it applies pressure to the brakes. My local dealer said that this is normal and he has owned 3 different years of Auroras. In all it is still a good recomendation to take the rotors off and have someone measure them for wear and tear and to see if they need replacing. Your local parts store that can resurface them should be able to check that for you. Hope that helps.